The present invention relates to fuel injector devices for internal combustion engines using an alternative fuel with respect to petrol or diesel oil, such as for instance methane, LPG, hydrogen or other fuels, either in gaseous or liquid state.
In internal combustion engines using alternative fuels such as those referred to above, the fuel is introduced into the intake manifold or engine cylinders by means of injector devices. Said injector devices are currently obtained from petrol injector devices. This is because engines using alternative fuels are not so widespread yet as to justify huge investments that would be required to back up designing activities dedicated to a new type of injector device. As a consequence, injector devices used until today in methane or LPG engines are the result of a compromise and therefore do not meet in an optimal way the specific requirements related to the injection of said alternative fuels. Namely, a main requirement is to adjust the injector device to working pressures related to the use of such fuels, which are far higher than the pressure at which petrol and diesel oil injectors work. For instance, a common petrol injector device injects petrol at a pressure of about 3–4 bars, whereas working pressures of LPG and methane are certainly above 10 bars. On the other hand, an injector device for a fuel such as LPG or methane does not have to meet other requirements that are specific for petrol injection, such as the one related to the particular shape of the injected spray (spray pattern) and to its granulometry. In the case of LPG or methane injection, adulterations of petrol injector devices aiming at obtaining shape and granulometry are useless, being it sufficient to meter the correct amount of fuel during injection.